A high-density input/output card (I/O card) is generally used in a data server. Electronic devices, such as chips, on an I/O card would generate a large amount of heat during operation. Such heat must be dissipated timely through a heat dissipation apparatus to avoid damaging the electronic component. The traditional approach is to arrange a heat dissipation apparatus over the chip. However, as the input/output card is generally mounted upside down on the main board, the cooling portions of the heat dissipation apparatus are located in a narrow space between the I/O card and the main board, which leads to a sharp reduction of the performance of the heat dissipation apparatus.